Post manual for v0.15.3

Author: alerque

static/manual/sile-latest.pdf

@@ -1 +1 @@
-sile-0.15.2.pdf
+sile-0.15.3.pdf

templates/partials/menu.html

@@ -7,7 +7,7 @@
       <li><a href="{{ get_url(path="@/examples/packages.md") }}">Packages</a></li>
     </ul>
   </li>
-  <li> <a href="{{ get_url(path="/manual/sile-0.15.2.pdf") }}">Manual (PDF)</a></li>
+  <li> <a href="{{ get_url(path="/manual/sile-0.15.3.pdf") }}">Manual (PDF)</a></li>
   <li> <a href="{{ get_url(path="/lua-api/") }}">Lua API (develop)</a></li>
   <li> <a href="{{ get_url(path="@/sil-grammar/index.md") }}">SIL Grammar</a></li>
   <li> <a href="https://github.com/sile-typesetter/sile/releases"><strong>Download</strong></a></li>